A Phytophthora sojae G-protein alpha subunit is involved in chemotaxis to soybean isoflavones.
For the soybean pathogen Phytophthora sojae, chemotaxis of zoospores to isoflavones is believed to be critical for recognition of the host and for initiating infection. However, the molecular mechanisms underlying this chemotaxis are largely unknown. To investigate the role of G-protein and calcium signaling in chemotaxis, we analyzed the expression of several genes known to be involved in these pathways and selected one that was specifically expressed in sporangia and zoospores but not in mycelium. This gene, named PsGPA1, is a single-copy gene in P. sojae and encodes a G-protein alpha subunit that shares 96% identity in amino acid sequence with that of Phytophthora infestans. To elucidate the function, expression of PsGPA1 was silenced by introducing antisense constructs into P. sojae. PsGPA1 silencing did not disturb hyphal growth or sporulation but severely affected zoospore behavior, including chemotaxis to the soybean isoflavone daidzein. Zoospore encystment and cyst germination were also altered, resulting in the inability of the PsGPA1-silenced mutants to infect soybean. In addition, the expressions of a calmodulin gene, PsCAM1, and two calcium- and calmodulin-dependent protein kinase genes, PsCMK3 and PsCMK4, were increased in the mutant zoospores, suggesting that PsGPA1 negatively regulates the calcium signaling pathways that are likely involved in zoospore chemotaxis.
Hua
Chenlei
C
Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China.
Wang
Yonglin
Y
Zheng
Xiaobo
X
Dou
Daolong
D
Zhang
Zhengguang
Z
Govers
Francine
F
Wang
Yuanchao
Y
D020418:Algal Proteins / Q000235:genetics / Q000378:metabolism*; D020013:Calcium Signaling; D002633:Chemotaxis; D044385:GTP-Binding Protein alpha Subunits / Q000235:genetics / Q000378:metabolism*; D018628:Gene Dosage; D015870:Gene Expression; D007529:Isoflavones / Q000378:metabolism*; D008969:Molecular Sequence Data; D010838:Phytophthora / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D010935:Plant Diseases / Q000469:parasitology*; D013025:Glycine max / Q000378:metabolism* / Q000469:parasitology; D013170:Spores / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology; D014774:Virulence
D020418:Algal Proteins; D044385:GTP-Binding Protein alpha Subunits; D007529:Isoflavones